Different types of battery cells, such as a round cell, a prismatic cell or a pouch cell are known. In the case of a round cell or a prismatic cell, the active material, containing the electrodes and separators, is generally rolled up into a coil and placed in a robust aluminum housing. In the case of the pouch cell, the individual layers of the active material are stacked or folded, and packaged into a flexible aluminum composite film.
In operation, a current flow, either a charge or discharge, generates heat due to both electrochemical and electrical impedance effects. Due to temperature limitations at both low and high temperatures it is desirable to control an operating temperature range for batteries to ensure optimal performance of the battery.
Various heat exchanger structures and battery unit arrangements have been developed for providing cooling (and/or heating) to thermally conductive batteries. For instance, it is known for heat to be dissipated or transported from (or to) the exterior surfaces of the battery housing by (i) exposing the external surfaces to circulating air or by (ii) pressing a chilled (or heated) surface, whether it be a fluid-carrying heat exchanger cooling plate or a non-fluid carrying metallic conduction plate either between or in contact with battery cell surfaces. When the battery cell surfaces are in contact with a chilled (or heated) surface, there is concern with regard to thermal contact resistance and thermal constriction resistance as well as the mechanical aspects of maintaining sufficient contact/pressure between the two, especially in the application of automotive power batteries. As well, the contacting surfaces themselves must be sufficiently conformal to allow for good thermal contact between the battery unit and the cooling plate. When the battery cell surfaces are cooled by exposing the surfaces to circulating air, the spacing-apart of individual battery units or cells results in increased space allowances. As well, this method has more limited cooling effects and also makes it more difficult to recover heat for uses in other vehicle systems. Accordingly, known methods for cooling batteries tend to have high costs, increased space and/or weight penalties, as well as high tolerance requirements, all of which are desirable to overcome.